Antifungal Therapy in Birds: Old Drugs in a New Jacket

First Documentation of Exophiala spp. Isolation in Psittaciformes

Several fungi species are reported to act as opportunistic agents of infection in avian species. After the isolation of Exophiala spp., a dematiaceous fungal pathogen associated with a mucosal lesion in a military macaw (Ara militar), samples were collected from another 24 birds of the order Psittaciformes to study the possibility of Exophiala spp. being part of the commensal microbiota of these animals or its possible association with other clinical conditions. Swab samples were collected from the trachea and/or choanae of the birds and inoculated in Sabouraud chloramphenicol agar for fungal isolation. After incubation, fungal species were identified through their macroscopic and microscopic morphology. The presence of Exophiala spp. was identified in 15 of the 25 birds sampled and no statistical association was found between the clinical record of the birds and the fungal isolation. Our results suggest that Exophiala spp. can colonize the upper respiratory airways of psittaciform birds and has a low pathogenic potential in these animals. To the authors’ knowledge, this is the first report of Exophiala spp. isolation from samples of the upper respiratory tract of Psittaciformes.

Diagnosis and treatment of Candida glabrata proventriculitis in an eclectus parrot (Eclectus roratus)

CASE DESCRIPTION

An 8-year-old sexually intact female eclectus parrot (Eclectus roratus) with a 4-day history of hyporexia and lethargy and a 1-day history of tenesmus was examined.

CLINICAL FINDINGS

Severe leukocytosis characterized by severe heterophilia and moderate monocytosis was present. Marked dilation of the proventriculus and ventriculus and ascites were identified by means of radiography, coelomic ultrasonography, and contrast-enhanced CT, with no clinically relevant motility noted on ultrasonography. Results of coelomic fluid analysis were consistent with pyogranulomatous effusion. Endoscopy of the upper gastrointestinal tract following proventricular and ventricular lavage showed a thick caseous plaque occupying 30% of the caudal proventricular mucosa. Abundant yeast organisms were evident during cytologic examination of a proventricular and ventricular wash sample, and fecal culture yielded Candida glabrata.

TREATMENT AND OUTCOME

The bird was treated with SC fluids, assisted feedings, nystatin, fluconazole, amoxicillin–clavulanic acid, enrofloxacin, gastroprotectants, maropitant, and analgesics and slowly improved during hospitalization. A marked decrease in proventricular dilation was evident on serial radiographs obtained over a 12-month period. One year after diagnosis, the bird was presented with a 1-week history of hyporexia and lethargy, and fecal culture grew C glabrata. Antifungal treatment was resumed for 3 months. The bird had no clinical signs of infection 16 months after this recurrence, and subsequent fecal cultures were negative for fungal growth.

CLINICAL RELEVANCE

Findings illustrate the importance of upper gastrointestinal endoscopy in diagnosing proventricular and ventricular dilation in birds and emphasize the need for long-term antifungal treatment and monitoring in birds with fungal infections.

Disposition of posaconazole after single oral administration in large falcons (Falco spp): Effect of meal and dosage and a non-compartmental model to predict effective dosage

Posaconazole has been used anecdotally to treat aspergillosis in falcons resistant to voriconazole. In human medicine, it is used prophylactically in immunosuppressed human subjects with invasive pulmonary aspergillosis. So far, no studies have been performed in birds. The aim of this study was to evaluate the in-vivo pharmacokinetic behavior of oral posaconazole after a single administration in six large falcons (i.e gyrfalcons, saker falcons). Posaconazole oral suspension (Noxafil, 40 mg/ml, Schering-Plough) was administered per os without meal in a single dosage of 12.5 mg/kg in 3 falcons. A comparison was done in two more falcons, one with a natural fatty meal at the same single dose, and one with a natural fatty meal and a higher dosage (20 mg/kg). Finally, six falcons received posaconazole pre-dissolved in corn oil with a natural low-fat meal in the higher single dose (20 mg/kg). No side effects were observed in the falcons in any of the experiments. In starved state posaconazole was poorly absorbed, more so than in other species. As expected, absorption of posaconazole was higher with the administration of meal or in the presence of plant (corn) oil, with a fourfold increase in apparent bioavailability. Despite the preferential absorption in the presence of fat, for both dosing schemes the AUC24 : MIC ratio was lower than described in human medicine to achieve a therapeutic effect. The AUCinf : MIC which is an indicator of efficacy after steady-state, while variable, did indicate that the drug is worth trying when susceptibility testing shows to be the only effective drug.

LAY ABSTRACT

The focus of this work is to determine the pharmacokinetic parameters of oral posaconazole in large falcons for the first time after a single dose. Posaconazole has higher bioavailability when administered with meal and fatty components. No adverse reactions have been observed. The ratio of the area under the curve (AUC24) to minimum inhibitory concentration was lower compared to the therapeutic level in human.

Aspergillosis in Wild Birds

The ubiquitous fungi belonging to the genus Aspergillus are able to proliferate in a large number of environments on organic substrates. The spores of these opportunistic pathogens, when inhaled, can cause serious and often fatal infections in a wide variety of captive and free-roaming wild birds. The relative importance of innate immunity and the level of exposure in the development of the disease can vary considerably between avian species and epidemiological situations. Given the low efficacy of therapeutic treatments, it is essential that breeders or avian practitioners know the conditions that favor the emergence of Aspergillosis in order to put adequate preventive measures in place.

Pharmacokinetics of voriconazole after a single intramuscular injection in large falcons (Falco spp.)

Voriconazole is one of the main azoles used to treat invasive aspergillosis in falconry raptors and birds. Despite the fact that there are studies for oral and intravenous use of voriconazole in birds, there are none for its effect after intramuscular use. Empirical use of intramuscular voriconazole in falcons, indicated quicker therapy response than the oral one. Aim of this study is to evaluate the in vivo pharmacokinetic disposition of injectable voriconazole after a single intramuscular injection in large falcons (i.e., Gyrfalcons, Saker falcons, Peregrine falcons). No clinical side effects were observed in the falcons. Absorption of voriconazole was rapid (0.5-2 hours) and reached a plasma level (>1 μg/ml) which is above the minimal inhibitory concentration (MIC) for all known Aspergillus strains. This level was maintained for 16 to 20 hours, thus indicating that a single injection of 12.5 mg/kg is not enough if T > MIC is taken into consideration. On a newer aspect, according to the AUC24 unbound: MIC parameter would be indicated that this dose would be rather sufficient for most Aspergillus strains.

Clinical Management of Avian Renal Disease

Treatment of avian renal disease relies on supportive care, such as fluid therapy and nutritional support. Analgesia and adaptations of the environment are indicated in cases of renal disease associated with painful joints. Other treatments vary with the underlying etiology and may include systemic antibiotics, antifungal therapy, vitamin A supplementation, or chelation therapy.

Application of different pharmacokinetic models to describe and predict pharmacokinetics of voriconazole in magellanic penguins following oral administration

Aspergillosis is a condition causing serious morbidity and mortality in captive penguins and other bird species. It can be treated with antifungal drugs, such as voriconazole. However, the pharmacokinetics of voriconazole are variable between different animal and bird species. Therefore, the pharmacokinetics of voriconazole were investigated in this study in Magellanic penguins. Pharmacokinetic models were constructed and applied to predict the pharmacokinetics of voriconazole during long-term treatment in Magellanic penguins, since the voriconazole treatment duration in chronic aspergillosis cases can last up to several months. Plasma voriconazole concentration-time data from adult Magellanic penguins (Spheniscus magellanicus; n = 15) following a single oral (PO) dose of either 2.5 mg/kg or 5 mg/kg in a herring in three separate study periods 7-12 months apart were collected. Mean plasma voriconazole concentrations were above the targeted MIC for Aspergillus fumigatus for 2 hr following a single 2.5 mg/kg voriconazole dose while the plasma concentrations exceeded the MIC for least 24 hr following a 5 mg/kg dose. Nonlinear mixed-effects modeling was used to fit two pharmacokinetic models, one with first-order and another with saturable elimination, to the single-dose data. Fits were good for both, as long as dose was included as a covariate for the first-order model so that clearance was lower and the half-life longer for animals receiving the 5 mg/kg dose. Although the single-dose data suggested saturated elimination at higher concentrations, the model with saturable elimination did not predict plasma voriconazole concentrations well for a clinical aspergillosis case receiving long-term treatment, possibly because of induction of metabolizing enzymes with chronic exposure. Pharmacokinetic models should accurately predict plasma drug concentrations for different dosage regimens in order to be applicable in the field. Future studies should focus on determining clearance at steady-state to be able to refine the pharmacokinetic models presented here and improve model performance for long-term oral voriconazole administration in Magellanic penguins.